The present invention relates to a coupling device for providing a friction joint between members.
Such devices are previously known, and generally at least one of the inner and the outer element consists of an axially slitted sleeve with a cylindrical surface, which contacts a corresponding surface on an adjacent member. The sleeve is deformed radially during the mounting procedure and provides a friction joint over the cylindrical surfaces. Such a friction joint can thus easily be established and released by axially displacing the elements provided with the tapered surfaces.
In order to obtain a sufficient surface pressure to establish a suitable force and torque transmitting ability in the friction joint, the axial force applied during the displacement has to be comparatively great and the cone angle in the tapered surfaces has to be rather small. It is an advantage if the coefficient of friction between the tapered contact surfaces is small, since thereby the axial force necessary to obtain a desired surface pressure will be moderate and it is known to provide the co-operating tapered surfaces with a low friction surface layer.
A desired result when applying e.g. polytetrafluoroethylene has only been achieved when both the tapered surfaces have been covered. This implies that complete devices are comparatively expensive.
The object of the present invention is to obtain a device of the kind stated in the introduction, which device can be produced simply and inexpensively, and with which a safe friction joint can be established by using a comparatively small axial force.
To this end, in accordance with the present invention, the coupling device comprises inner and outer elements each having confronting complementary tapered surfaces, which elements are actuatable axially relative to one another in a direction parallel to the cone axes of the tapered surfaces to effect radial deformation of at least one of the elements. The tapered surface of one of the elements is continuous and the complementary tapered surface of the other element has at least one circumferential groove formed therein, thereby providing only contact between the surfaces at other than the groove location and thus reducing the active contact surface area between the tapered surfaces. The tapered surface of the one element is provided with a deformable friction reducing material which transfers to the initially uncovered tapered surface of the other element during axial displacement of the elements.
The separate elements constituting the device can be manufactured by e.g. automatic turning, and only one tapered surface has to be covered by a friction reducing material during the manufacturing process.